3. Homeostasis Flashcards

1
Q

Define Homeostasis

A

Homeostasis is the maintenence of a constant internal environment

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2
Q

Define Negative feedback control mechanism

A

This is when a deviation from a set point/norm value will result in effectors being activated to restore the set point value. (eg effectors being muscle or gland)

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3
Q

Give an example of a negative feedback control mechanism

A

Control of core body temperature via thermoregulation

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4
Q

Define positive feedback mechanism

A

An initial stimulus produces a response that exaggerates or enhances the change in the original conditions, rather than opposing it. I.e a deviation from the set point results in processes that enhance that deviation further from the norm

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5
Q

Give an example of a positive feedback mechanism

A

Childbirth

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6
Q

What are the two different systems employed in homeostatic regulation

A

Autoregulation

Extrinsic regulation

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7
Q

Define autoregulation

A

This describes local level, cellular/tissue level response to environmental change. Eg a change in the oxygen concentration will triger chemicals that widen/dilate blood vessels.

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8
Q

List the three components of a homeostatic regulatory mechanism

A

Receptor, detects environmental stimuli

Control center, recieves and processes information

Effector, a cell or organ which responds to commands from control centre

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9
Q

Define extrinsic regulation

A

This involves nervous/endocrine control. For example, during exercise, the nervous system issues commands to increase heart rate so blood circulates faster

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10
Q

Why is homeostatic regulation important

A

Because it is important to prevent harmful changes in body tissue fluid composition.

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11
Q

Define set point

A

This is a value at which a controlled variable should be maintained.

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12
Q

Define negative feedback control

A

aims to maintain a controlled variable at its set point. Controlled variable is some aspect of the internal environment, like blood pressure or plasma

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13
Q

Describe briefly the process of thermoregulation

A

The set point core body temperature is 37 degrees.
If temperature rises above core temp, receptors fire to the control centre.

Control centre fires to 2 target effectors.

1) Muscle tissue lining the walls of the blood vessels
2) sweat glands.

Blood vessels dilate to increase the skin surface blood flow.

Skin acts as a radiator by loosing heat to environment via sweat. Sweat evaporates.

As the set point for temp is restored, blood flow to skin returns to normal levels.

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14
Q

Explain the two ways in which heat loss is achieved in the event of elevated core body temperature ( >37.2 degs)

A

Increased blood flow to skin surface via skin capillaries.

Increased sweating

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15
Q

The control of body temperature can also be thought of as a thermostat. Describe this process

A

Set point = normal room temp
Stimulus = room temperature rises (deviation from sp)
Receptor = thermometer (detects change and sends info to control centre)

Control centre = Thermostat, sends commands to the effector to switch on

Effector = AC. unit, which turns on. effector then acts to lower the temp, and restore the room temp to within normal range.

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16
Q

Give an example of an effector

A

muscle or gland

17
Q

Give an example of a receptor

A

sensory receptor cells

18
Q

Describe how blood pressure is regulated via homeostasis

A

Baroreceptors detect fall in blood pressure

baroreceptors fire implumses to the c.c via the Glossopharyngeal nerve in the medulla oblongata

Medulla fires to the heart and blood vessels via autonomic to increase cardiac output and vasoconstriction

Effectors = heart and blood vessels which increase blood pressure and vasoconsriction

19
Q

State the name of the nerve that baroreceptors fire impulses along to the medulla oblongata

A

Glossopharyngeal nerve

20
Q

In control of blood pressure, the medulla oblongata fires impulses to the heart and blood vessels along which nerves

A

The autonomic nerves

21
Q

Explain positive feedback mechanisms

A

This is where initial stimulus causes a response which continually reinforces itself.

22
Q

Give some examples of positive feedback mechanisms

A

Action potentials in nerves

Ovulation

Blood Clotting

23
Q

Explain how the process of clotting is a positive feedback mechanism

A

Damage to blood vessel causes:

activation of clotting factors
causes activationof thrombin
causes formation of a blood clot

24
Q

Which type of response is the nervous system involved in

A

Rapid, short term effects that last seconds usually

25
Q

Which type of responses/effects is the endocrine system involved in

A

Long term effects.

examples include growth and metabolism

26
Q

What are thyroid hormones involved in

A

Metabolism control

27
Q

What are the features of nerves from the autonomic nervous system

A

CNS has a preganglionic neuron.
Peripheral ganglion is called a postganglionic neuron.
these both fire to a target cell.

Contains Parasympathetic and sympathetic nervous system

28
Q

Describe the Parasympathetic Nerve

A
  • Preganglionic neuron coming out of the cranial and sacral vertebrae regions
  • Preganglionic fibres are long. Postganglionic fibres are short.
  • Preganglionic fibres releases Acetylcholine (ganglionic transmitter) at the synapse. This binds to the nicotinic receptor on the short postganglionic fibre which releases acetylcholine (neurotransmitter) that activates muscarinic receptor on the target organ
29
Q

Describe the Sympathetic Nerve

A
  • Preganglionic neuron out of the spinal cord at the thoracic and lumbar vertebrae regions.
  • Preganglionic fibres are short. Postganglionic fibres are long.
  • Pre-g fibre release acetylcholine (ganglionic transmitter) at the synapse.
  • Nicotinic receptor is activated.
  • Impulse travels along long Post-g fibre and releases norepinephrine/noradrenaline (neurotransmitter).
  • Alpha & Beta adrenergic receptors on target organ are activated.
30
Q

How is adrenaline/ epinephrine produced?

A

Adrenal medulla receives impulse from pre-g sympathetic fibre into the internal adrenal medulla.

Acetylcholine is released, which stimulates nicotinic receptors on chromaffin cells,

Chromaffin cells produce and release epinephrine or adrenaline into the circulation.

Adrenaline has similar effects to noradrenaline

31
Q

Define Efferent Pathways

A

Efferent pathwayscarry signals away from the central nervous system. Essentially, they are signals that your brain sends to tell your body to do something, like blinking.

32
Q

Define Afferent Pathways

A

Afferent signals come from outside stimuli and tell your brain what they are sensing, such as temperature.